The present invention relates generally to a poultice method for removing chemical spills from porous surfaces such as construction materials, including concrete, soil, road beds and the like, and more particularly to a method for cleaning up spills of polychlorinated biphenyls (PCBs) and PCB-contaminated transformer oil from such surfaces.
In addition to accidental chemical spills, many instances of indiscriminate disposal of chemical wastes along road beds, in land fills and elsewhere have been reported over the last several years, and concern has grown over the potential harm to public health and the environment resulting from such occurences. Considerable effort is required in cleaning up chemical substances accidentally spilled or improperly disposed of, since the chemicals often become absorbed in the porous surfaces on which they are spilled. The situation is especially aggravated when the spilled chemical is a toxic material.
Present clean-up methods for toxic chemical spills on porous substrates frequently involve extensive excavation or destruction of the porous surface. These methods are quite expensive and not always effective. Moreover, even when the site of the spill is cleaned up, there remains the problem of disposing of the toxic chemical substance and debris associated therewith in a safe and effective manner.
Halogenated organic compounds are particularly difficult to dispose of because of the highly stable nature of the carbon-halogen bonds present therein. Compounds such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), decachlorooctahydro-1,3,4-metheno-2H-cyclobuta-[c,d]-pentalen-2-one (Kepone.RTM.), and 2,4,5-trichlorophenoxyacetic acid, (2,4,5-T), which have been found to be persistent environmental toxins, are not only resistant to biodegradation, they cannot be degraded in a practical and effective manner by any of the well known chemical decomposition methods. In most cases, known decomposition methods such as chlorolysis, catalytic dehydrohalogenation, molten salt reactions, ozone reactions and alkali metal reduction achieve only partial dehalogenation of such compounds. Moreover, these prior art methods typically involve one or more drawbacks, such as the use of expensive reagents, extensive temperature control, inert atmospheres, complex apparatus and/or substantial energy consumption which would make it difficult to utilize these methods in disposing of halogenated organic compounds present in the porous surfaces described above.
During the past several years, there has been developed at the Franklin Research Center of the Franklin Institute, Philadelphia, Pa., a system for stripping the chlorine substituents from various halogenated organic compounds, including PCBs, thus rendering them non-toxic and readily disposable. More specifically, Pytlewski, Krevitz and Smith, in their U.S. patent application Ser. No. 158,359, filed June 11, 1980, now U.S. Pat. No. 4,337,368, disclose and claim a method for the decomposition of halogenated organic compounds, which represents a significant advance over the aforementioned decomposition methods of the prior art. The decomposition reagent used in practicing the method of Pytlewski et al. is formed from the reaction between an alkali metal, a liquid reactant, such as polyglycol or a polyglycol monalkyl ether, and oxygen. This reagent produces substantially complete dehalogenation simply by mixing it with the halogenated compound in the presence of oxygen.
In U.S. patent application Ser. No. 240,622, filed Mar. 5, 1981, now U.S. Pat. No. 4,400,522, there is described and claimed another invention by Pytlewski et al. based on the discovery that substantially complete dehalogenation of halogenated organic compounds may be carried out using a reagent produced by the reaction of an alkali metal hydroxide (rather than an alkali metal), a liquid reactant, such as a polyglycol or a polyglycol monalkyl ether, and oxygen. This decomposition reagent gives results which are comparable to those obtained with the method described in the earlier filed application of Pytlewski et al. referred to above.
The reagents of the aforesaid patent and application are collectively referred to hereinafter as NaPEG reagents, or simply NaPEG.
The development of the NaPEG reagents has made it possible to remove halogenated organic compounds from fluids contaminated therewith, as well as to decompose such compounds in concentrated form in a safe, efficient and effective manner.